xenbus.c

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/*
 * PCI Backend Xenbus Setup - handles setup with frontend and xend
 *
 *   Author: Ryan Wilson <[email protected]>
 */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/workqueue.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <asm/xen/pci.h>
#include "pciback.h"

#define INVALID_EVTCHN_IRQ  (-1)
struct workqueue_struct *xen_pcibk_wq;

static bool __read_mostly passthrough;
module_param(passthrough, bool, S_IRUGO);
MODULE_PARM_DESC(passthrough,
    "Option to specify how to export PCI topology to guest:\n"\
    " 0 - (default) Hide the true PCI topology and makes the frontend\n"\
    "   there is a single PCI bus with only the exported devices on it.\n"\
    "   For example, a device at 03:05.0 will be re-assigned to 00:00.0\n"\
    "   while second device at 02:1a.1 will be re-assigned to 00:01.1.\n"\
    " 1 - Passthrough provides a real view of the PCI topology to the\n"\
    "   frontend (for example, a device at 06:01.b will still appear at\n"\
    "   06:01.b to the frontend). This is similar to how Xen 2.0.x\n"\
    "   exposed PCI devices to its driver domains. This may be required\n"\
    "   for drivers which depend on finding their hardward in certain\n"\
    "   bus/slot locations.");

static struct xen_pcibk_device *alloc_pdev(struct xenbus_device *xdev)
{
    struct xen_pcibk_device *pdev;

    pdev = kzalloc(sizeof(struct xen_pcibk_device), GFP_KERNEL);
    if (pdev == NULL)
        goto out;
    dev_dbg(&xdev->dev, "allocated pdev @ 0x%p\n", pdev);

    pdev->xdev = xdev;
    dev_set_drvdata(&xdev->dev, pdev);

    mutex_init(&pdev->dev_lock);

    pdev->sh_info = NULL;
    pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
    pdev->be_watching = 0;

    INIT_WORK(&pdev->op_work, xen_pcibk_do_op);

    if (xen_pcibk_init_devices(pdev)) {
        kfree(pdev);
        pdev = NULL;
    }
out:
    return pdev;
}

static void xen_pcibk_disconnect(struct xen_pcibk_device *pdev)
{
    mutex_lock(&pdev->dev_lock);
    /* Ensure the guest can't trigger our handler before removing devices */
    if (pdev->evtchn_irq != INVALID_EVTCHN_IRQ) {
        unbind_from_irqhandler(pdev->evtchn_irq, pdev);
        pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
    }

    /* If the driver domain started an op, make sure we complete it
     * before releasing the shared memory */

    /* Note, the workqueue does not use spinlocks at all.*/
    flush_workqueue(xen_pcibk_wq);

    if (pdev->sh_info != NULL) {
        xenbus_unmap_ring_vfree(pdev->xdev, pdev->sh_info);
        pdev->sh_info = NULL;
    }
    mutex_unlock(&pdev->dev_lock);
}

static void free_pdev(struct xen_pcibk_device *pdev)
{
    if (pdev->be_watching) {
        unregister_xenbus_watch(&pdev->be_watch);
        pdev->be_watching = 0;
    }

    xen_pcibk_disconnect(pdev);

    xen_pcibk_release_devices(pdev);

    dev_set_drvdata(&pdev->xdev->dev, NULL);
    pdev->xdev = NULL;

    kfree(pdev);
}

static int xen_pcibk_do_attach(struct xen_pcibk_device *pdev, int gnt_ref,
                 int remote_evtchn)
{
    int err = 0;
    void *vaddr;

    dev_dbg(&pdev->xdev->dev,
        "Attaching to frontend resources - gnt_ref=%d evtchn=%d\n",
        gnt_ref, remote_evtchn);

    err = xenbus_map_ring_valloc(pdev->xdev, gnt_ref, &vaddr);
    if (err < 0) {
        xenbus_dev_fatal(pdev->xdev, err,
                "Error mapping other domain page in ours.");
        goto out;
    }

    pdev->sh_info = vaddr;

    err = bind_interdomain_evtchn_to_irqhandler(
        pdev->xdev->otherend_id, remote_evtchn, xen_pcibk_handle_event,
        0, DRV_NAME, pdev);
    if (err < 0) {
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error binding event channel to IRQ");
        goto out;
    }
    pdev->evtchn_irq = err;
    err = 0;

    dev_dbg(&pdev->xdev->dev, "Attached!\n");
out:
    return err;
}

static int xen_pcibk_attach(struct xen_pcibk_device *pdev)
{
    int err = 0;
    int gnt_ref, remote_evtchn;
    char *magic = NULL;


    mutex_lock(&pdev->dev_lock);
    /* Make sure we only do this setup once */
    if (xenbus_read_driver_state(pdev->xdev->nodename) !=
        XenbusStateInitialised)
        goto out;

    /* Wait for frontend to state that it has published the configuration */
    if (xenbus_read_driver_state(pdev->xdev->otherend) !=
        XenbusStateInitialised)
        goto out;

    dev_dbg(&pdev->xdev->dev, "Reading frontend config\n");

    err = xenbus_gather(XBT_NIL, pdev->xdev->otherend,
                "pci-op-ref", "%u", &gnt_ref,
                "event-channel", "%u", &remote_evtchn,
                "magic", NULL, &magic, NULL);
    if (err) {
        /* If configuration didn't get read correctly, wait longer */
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error reading configuration from frontend");
        goto out;
    }

    if (magic == NULL || strcmp(magic, XEN_PCI_MAGIC) != 0) {
        xenbus_dev_fatal(pdev->xdev, -EFAULT,
                 "version mismatch (%s/%s) with pcifront - "
                 "halting " DRV_NAME,
                 magic, XEN_PCI_MAGIC);
        goto out;
    }

    err = xen_pcibk_do_attach(pdev, gnt_ref, remote_evtchn);
    if (err)
        goto out;

    dev_dbg(&pdev->xdev->dev, "Connecting...\n");

    err = xenbus_switch_state(pdev->xdev, XenbusStateConnected);
    if (err)
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error switching to connected state!");

    dev_dbg(&pdev->xdev->dev, "Connected? %d\n", err);
out:
    mutex_unlock(&pdev->dev_lock);

    kfree(magic);

    return err;
}

static int xen_pcibk_publish_pci_dev(struct xen_pcibk_device *pdev,
                   unsigned int domain, unsigned int bus,
                   unsigned int devfn, unsigned int devid)
{
    int err;
    int len;
    char str[64];

    len = snprintf(str, sizeof(str), "vdev-%d", devid);
    if (unlikely(len >= (sizeof(str) - 1))) {
        err = -ENOMEM;
        goto out;
    }

    /* Note: The PV protocol uses %02x, don't change it */
    err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, str,
                "%04x:%02x:%02x.%02x", domain, bus,
                PCI_SLOT(devfn), PCI_FUNC(devfn));

out:
    return err;
}

static int xen_pcibk_export_device(struct xen_pcibk_device *pdev,
                 int domain, int bus, int slot, int func,
                 int devid)
{
    struct pci_dev *dev;
    int err = 0;

    dev_dbg(&pdev->xdev->dev, "exporting dom %x bus %x slot %x func %x\n",
        domain, bus, slot, func);

    dev = pcistub_get_pci_dev_by_slot(pdev, domain, bus, slot, func);
    if (!dev) {
        err = -EINVAL;
        xenbus_dev_fatal(pdev->xdev, err,
                 "Couldn't locate PCI device "
                 "(%04x:%02x:%02x.%d)! "
                 "perhaps already in-use?",
                 domain, bus, slot, func);
        goto out;
    }

    err = xen_pcibk_add_pci_dev(pdev, dev, devid,
                    xen_pcibk_publish_pci_dev);
    if (err)
        goto out;

    dev_dbg(&dev->dev, "registering for %d\n", pdev->xdev->otherend_id);
    if (xen_register_device_domain_owner(dev,
                         pdev->xdev->otherend_id) != 0) {
        dev_err(&dev->dev, "Stealing ownership from dom%d.\n",
            xen_find_device_domain_owner(dev));
        xen_unregister_device_domain_owner(dev);
        xen_register_device_domain_owner(dev, pdev->xdev->otherend_id);
    }

    /* TODO: It'd be nice to export a bridge and have all of its children
     * get exported with it. This may be best done in xend (which will
     * have to calculate resource usage anyway) but we probably want to
     * put something in here to ensure that if a bridge gets given to a
     * driver domain, that all devices under that bridge are not given
     * to other driver domains (as he who controls the bridge can disable
     * it and stop the other devices from working).
     */
out:
    return err;
}

static int xen_pcibk_remove_device(struct xen_pcibk_device *pdev,
                 int domain, int bus, int slot, int func)
{
    int err = 0;
    struct pci_dev *dev;

    dev_dbg(&pdev->xdev->dev, "removing dom %x bus %x slot %x func %x\n",
        domain, bus, slot, func);

    dev = xen_pcibk_get_pci_dev(pdev, domain, bus, PCI_DEVFN(slot, func));
    if (!dev) {
        err = -EINVAL;
        dev_dbg(&pdev->xdev->dev, "Couldn't locate PCI device "
            "(%04x:%02x:%02x.%d)! not owned by this domain\n",
            domain, bus, slot, func);
        goto out;
    }

    dev_dbg(&dev->dev, "unregistering for %d\n", pdev->xdev->otherend_id);
    xen_unregister_device_domain_owner(dev);

    xen_pcibk_release_pci_dev(pdev, dev);

out:
    return err;
}

static int xen_pcibk_publish_pci_root(struct xen_pcibk_device *pdev,
                    unsigned int domain, unsigned int bus)
{
    unsigned int d, b;
    int i, root_num, len, err;
    char str[64];

    dev_dbg(&pdev->xdev->dev, "Publishing pci roots\n");

    err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
               "root_num", "%d", &root_num);
    if (err == 0 || err == -ENOENT)
        root_num = 0;
    else if (err < 0)
        goto out;

    /* Verify that we haven't already published this pci root */
    for (i = 0; i < root_num; i++) {
        len = snprintf(str, sizeof(str), "root-%d", i);
        if (unlikely(len >= (sizeof(str) - 1))) {
            err = -ENOMEM;
            goto out;
        }

        err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
                   str, "%x:%x", &d, &b);
        if (err < 0)
            goto out;
        if (err != 2) {
            err = -EINVAL;
            goto out;
        }

        if (d == domain && b == bus) {
            err = 0;
            goto out;
        }
    }

    len = snprintf(str, sizeof(str), "root-%d", root_num);
    if (unlikely(len >= (sizeof(str) - 1))) {
        err = -ENOMEM;
        goto out;
    }

    dev_dbg(&pdev->xdev->dev, "writing root %d at %04x:%02x\n",
        root_num, domain, bus);

    err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, str,
                "%04x:%02x", domain, bus);
    if (err)
        goto out;

    err = xenbus_printf(XBT_NIL, pdev->xdev->nodename,
                "root_num", "%d", (root_num + 1));

out:
    return err;
}

static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev)
{
    int err = 0;
    int num_devs;
    int domain, bus, slot, func;
    int substate;
    int i, len;
    char state_str[64];
    char dev_str[64];


    dev_dbg(&pdev->xdev->dev, "Reconfiguring device ...\n");

    mutex_lock(&pdev->dev_lock);
    /* Make sure we only reconfigure once */
    if (xenbus_read_driver_state(pdev->xdev->nodename) !=
        XenbusStateReconfiguring)
        goto out;

    err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d",
               &num_devs);
    if (err != 1) {
        if (err >= 0)
            err = -EINVAL;
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error reading number of devices");
        goto out;
    }

    for (i = 0; i < num_devs; i++) {
        len = snprintf(state_str, sizeof(state_str), "state-%d", i);
        if (unlikely(len >= (sizeof(state_str) - 1))) {
            err = -ENOMEM;
            xenbus_dev_fatal(pdev->xdev, err,
                     "String overflow while reading "
                     "configuration");
            goto out;
        }
        err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, state_str,
                   "%d", &substate);
        if (err != 1)
            substate = XenbusStateUnknown;

        switch (substate) {
        case XenbusStateInitialising:
            dev_dbg(&pdev->xdev->dev, "Attaching dev-%d ...\n", i);

            len = snprintf(dev_str, sizeof(dev_str), "dev-%d", i);
            if (unlikely(len >= (sizeof(dev_str) - 1))) {
                err = -ENOMEM;
                xenbus_dev_fatal(pdev->xdev, err,
                         "String overflow while "
                         "reading configuration");
                goto out;
            }
            err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
                       dev_str, "%x:%x:%x.%x",
                       &domain, &bus, &slot, &func);
            if (err < 0) {
                xenbus_dev_fatal(pdev->xdev, err,
                         "Error reading device "
                         "configuration");
                goto out;
            }
            if (err != 4) {
                err = -EINVAL;
                xenbus_dev_fatal(pdev->xdev, err,
                         "Error parsing pci device "
                         "configuration");
                goto out;
            }

            err = xen_pcibk_export_device(pdev, domain, bus, slot,
                            func, i);
            if (err)
                goto out;

            /* Publish pci roots. */
            err = xen_pcibk_publish_pci_roots(pdev,
                        xen_pcibk_publish_pci_root);
            if (err) {
                xenbus_dev_fatal(pdev->xdev, err,
                         "Error while publish PCI root"
                         "buses for frontend");
                goto out;
            }

            err = xenbus_printf(XBT_NIL, pdev->xdev->nodename,
                        state_str, "%d",
                        XenbusStateInitialised);
            if (err) {
                xenbus_dev_fatal(pdev->xdev, err,
                         "Error switching substate of "
                         "dev-%d\n", i);
                goto out;
            }
            break;

        case XenbusStateClosing:
            dev_dbg(&pdev->xdev->dev, "Detaching dev-%d ...\n", i);

            len = snprintf(dev_str, sizeof(dev_str), "vdev-%d", i);
            if (unlikely(len >= (sizeof(dev_str) - 1))) {
                err = -ENOMEM;
                xenbus_dev_fatal(pdev->xdev, err,
                         "String overflow while "
                         "reading configuration");
                goto out;
            }
            err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
                       dev_str, "%x:%x:%x.%x",
                       &domain, &bus, &slot, &func);
            if (err < 0) {
                xenbus_dev_fatal(pdev->xdev, err,
                         "Error reading device "
                         "configuration");
                goto out;
            }
            if (err != 4) {
                err = -EINVAL;
                xenbus_dev_fatal(pdev->xdev, err,
                         "Error parsing pci device "
                         "configuration");
                goto out;
            }

            err = xen_pcibk_remove_device(pdev, domain, bus, slot,
                            func);
            if (err)
                goto out;

            /* TODO: If at some point we implement support for pci
             * root hot-remove on pcifront side, we'll need to
             * remove unnecessary xenstore nodes of pci roots here.
             */

            break;

        default:
            break;
        }
    }

    err = xenbus_switch_state(pdev->xdev, XenbusStateReconfigured);
    if (err) {
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error switching to reconfigured state!");
        goto out;
    }

out:
    mutex_unlock(&pdev->dev_lock);
    return 0;
}

static void xen_pcibk_frontend_changed(struct xenbus_device *xdev,
                     enum xenbus_state fe_state)
{
    struct xen_pcibk_device *pdev = dev_get_drvdata(&xdev->dev);

    dev_dbg(&xdev->dev, "fe state changed %d\n", fe_state);

    switch (fe_state) {
    case XenbusStateInitialised:
        xen_pcibk_attach(pdev);
        break;

    case XenbusStateReconfiguring:
        xen_pcibk_reconfigure(pdev);
        break;

    case XenbusStateConnected:
        /* pcifront switched its state from reconfiguring to connected.
         * Then switch to connected state.
         */
        xenbus_switch_state(xdev, XenbusStateConnected);
        break;

    case XenbusStateClosing:
        xen_pcibk_disconnect(pdev);
        xenbus_switch_state(xdev, XenbusStateClosing);
        break;

    case XenbusStateClosed:
        xen_pcibk_disconnect(pdev);
        xenbus_switch_state(xdev, XenbusStateClosed);
        if (xenbus_dev_is_online(xdev))
            break;
        /* fall through if not online */
    case XenbusStateUnknown:
        dev_dbg(&xdev->dev, "frontend is gone! unregister device\n");
        device_unregister(&xdev->dev);
        break;

    default:
        break;
    }
}

static int xen_pcibk_setup_backend(struct xen_pcibk_device *pdev)
{
    /* Get configuration from xend (if available now) */
    int domain, bus, slot, func;
    int err = 0;
    int i, num_devs;
    char dev_str[64];
    char state_str[64];

    mutex_lock(&pdev->dev_lock);
    /* It's possible we could get the call to setup twice, so make sure
     * we're not already connected.
     */
    if (xenbus_read_driver_state(pdev->xdev->nodename) !=
        XenbusStateInitWait)
        goto out;

    dev_dbg(&pdev->xdev->dev, "getting be setup\n");

    err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d",
               &num_devs);
    if (err != 1) {
        if (err >= 0)
            err = -EINVAL;
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error reading number of devices");
        goto out;
    }

    for (i = 0; i < num_devs; i++) {
        int l = snprintf(dev_str, sizeof(dev_str), "dev-%d", i);
        if (unlikely(l >= (sizeof(dev_str) - 1))) {
            err = -ENOMEM;
            xenbus_dev_fatal(pdev->xdev, err,
                     "String overflow while reading "
                     "configuration");
            goto out;
        }

        err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, dev_str,
                   "%x:%x:%x.%x", &domain, &bus, &slot, &func);
        if (err < 0) {
            xenbus_dev_fatal(pdev->xdev, err,
                     "Error reading device configuration");
            goto out;
        }
        if (err != 4) {
            err = -EINVAL;
            xenbus_dev_fatal(pdev->xdev, err,
                     "Error parsing pci device "
                     "configuration");
            goto out;
        }

        err = xen_pcibk_export_device(pdev, domain, bus, slot, func, i);
        if (err)
            goto out;

        /* Switch substate of this device. */
        l = snprintf(state_str, sizeof(state_str), "state-%d", i);
        if (unlikely(l >= (sizeof(state_str) - 1))) {
            err = -ENOMEM;
            xenbus_dev_fatal(pdev->xdev, err,
                     "String overflow while reading "
                     "configuration");
            goto out;
        }
        err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, state_str,
                    "%d", XenbusStateInitialised);
        if (err) {
            xenbus_dev_fatal(pdev->xdev, err, "Error switching "
                     "substate of dev-%d\n", i);
            goto out;
        }
    }

    err = xen_pcibk_publish_pci_roots(pdev, xen_pcibk_publish_pci_root);
    if (err) {
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error while publish PCI root buses "
                 "for frontend");
        goto out;
    }

    err = xenbus_switch_state(pdev->xdev, XenbusStateInitialised);
    if (err)
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error switching to initialised state!");

out:
    mutex_unlock(&pdev->dev_lock);
    if (!err)
        /* see if pcifront is already configured (if not, we'll wait) */
        xen_pcibk_attach(pdev);
    return err;
}

static void xen_pcibk_be_watch(struct xenbus_watch *watch,
                 const char **vec, unsigned int len)
{
    struct xen_pcibk_device *pdev =
        container_of(watch, struct xen_pcibk_device, be_watch);

    switch (xenbus_read_driver_state(pdev->xdev->nodename)) {
    case XenbusStateInitWait:
        xen_pcibk_setup_backend(pdev);
        break;

    default:
        break;
    }
}

static int xen_pcibk_xenbus_probe(struct xenbus_device *dev,
                const struct xenbus_device_id *id)
{
    int err = 0;
    struct xen_pcibk_device *pdev = alloc_pdev(dev);

    if (pdev == NULL) {
        err = -ENOMEM;
        xenbus_dev_fatal(dev, err,
                 "Error allocating xen_pcibk_device struct");
        goto out;
    }

    /* wait for xend to configure us */
    err = xenbus_switch_state(dev, XenbusStateInitWait);
    if (err)
        goto out;

    /* watch the backend node for backend configuration information */
    err = xenbus_watch_path(dev, dev->nodename, &pdev->be_watch,
                xen_pcibk_be_watch);
    if (err)
        goto out;

    pdev->be_watching = 1;

    /* We need to force a call to our callback here in case
     * xend already configured us!
     */
    xen_pcibk_be_watch(&pdev->be_watch, NULL, 0);

out:
    return err;
}

static int xen_pcibk_xenbus_remove(struct xenbus_device *dev)
{
    struct xen_pcibk_device *pdev = dev_get_drvdata(&dev->dev);

    if (pdev != NULL)
        free_pdev(pdev);

    return 0;
}

static const struct xenbus_device_id xen_pcibk_ids[] = {
    {"pci"},
    {""},
};

static DEFINE_XENBUS_DRIVER(xen_pcibk, DRV_NAME,
    .probe          = xen_pcibk_xenbus_probe,
    .remove         = xen_pcibk_xenbus_remove,
    .otherend_changed   = xen_pcibk_frontend_changed,
);

const struct xen_pcibk_backend *__read_mostly xen_pcibk_backend;

int __init xen_pcibk_xenbus_register(void)
{
    xen_pcibk_wq = create_workqueue("xen_pciback_workqueue");
    if (!xen_pcibk_wq) {
        printk(KERN_ERR "%s: create"
            "xen_pciback_workqueue failed\n", __func__);
        return -EFAULT;
    }
    xen_pcibk_backend = &xen_pcibk_vpci_backend;
    if (passthrough)
        xen_pcibk_backend = &xen_pcibk_passthrough_backend;
    pr_info(DRV_NAME ": backend is %s\n", xen_pcibk_backend->name);
    return xenbus_register_backend(&xen_pcibk_driver);
}

void __exit xen_pcibk_xenbus_unregister(void)
{
    destroy_workqueue(xen_pcibk_wq);
    xenbus_unregister_driver(&xen_pcibk_driver);
}